Arsine Complexes Research Articles

Contrasting Photochemical and Thermal Catalysis by Ruthenium Arsine Complexes Revealed by Parahydrogen Enhanced NMR Spectroscopy

AbstractThe thermal and photochemical reactivity of Ru(CO)3(dpae) (1) and Ru(CO)2(dpae)(PPh3) (2) towards H2 and diphenylacetylene is described. These reactions are monitored by NMR spectroscopy in conjunction with the parahydrogen induced polarisation (PHIP) effect, spatially resolved chemical shift imaging and the Only Parahydrogen Spectroscopy (OPSY) signal filtering method. The results are supported by DFT. The thermal and photochemical reactions of 1 with H2 proceed by CO loss and form Ru(H)2(CO)2(dpae) (3). 1 catalyses the formation of 1,2 diphenylethane, cis‐ and trans‐stilbene, and 1,2,3,4 tetraphenylbutadiene under 325 nm irradiation at 295 K in a reaction where Ru(CO)2(dpae)(η2‐CHPh=CPhCPh=CHPh) forms. When the same reaction is monitored under thermal conditions at 333 K the η2‐diene complex is no longer detected but hydride containing Ru(CHPhCH2Ph)(H)(CO)2(dpae) and Ru(CO)2(dpae)(trans‐stilbene) are seen. For 1, the photochemical promotion of hydrogenation through 325 nm irradiation results in an approximate 5.5‐fold increase in turnover at 333 K when compared to no irradiation. In contrast, 2 reacts thermally with H2 at 295 K through PPh3 and CO loss with both Ru(H)2(CO)(dpae)(solvent) and 3 being detected. Under irradiation, CO loss dominates and two isomers of Ru(H)2(CO)(dpae)(PPh3) form. While 2 forms the same 4 organic products at 295 K and a second isomer of Ru(CHPhCH2Ph)(H)(CO)2(dpae) alongside the diene complex no photochemical promotion of hydrogenation is observed.

Tertiary Phosphine and Arsine Complexes of Phosphorus Pentafluoride: Synthesis, Properties, and Electronic Structures.

The reaction of PMe3 or PPh3 with PF5 in anhydrous CH2Cl2 or hexane forms the white, moisture-sensitive complexes [PF5(PR3)] (R = Me, Ph). Similar reactions involving the diphosphines o-C6H4(PR2)2 afford the complexes [PF4{o-C6H4(PR2)2}][PF6]. The X-ray structures of [PF5(PR3)] and [PF4{o-C6H4(PMe2)2}][PF6] show pseudo-octahedral fluorophosphorus centers. Multinuclear NMR spectra (1H, 19F{1H}, 31P{1H}) show that in solution in CH2Cl2/CD2Cl2 the structures determined crystallographically are the only species present for [PF5(PMe3)] and [PF4{o-C6H4(PMe2)2}][PF6] but that [PF5(PPh3)] and [PF4{o-C6H4(PPh2)2}][PF6] exhibit reversible dissociation of the phosphine at ambient temperatures, although exchange slows at low temperatures. The complex 19F{1H} and 31P{1H} NMR spectra have been analyzed, including those of the cation [PF4{o-C6H4(PMe2)2}]+, which is a second-order AA'XX'B2M spin system. The unstable [PF5(AsMe3)], which decomposes in a few hours at ambient temperatures, has also been isolated and spectroscopically characterized; neither AsPh3 nor SbEt3 forms similar complexes. The electronic structures of the PF5 complexes have been explored by DFT calculations. The DFT optimized geometries for [PF5(PMe3)], [PF5(PPh3)], and [PF4{o-C6H4(PMe2)2}]+ are in good agreement with their respective crystal structure geometries. DFT calculations on the PF5-L complexes reveal the P-L bond strength falls with L in the order PMe3 > PPh3 > AsMe3, consistent with the experimentally observed stabilities, and in the PF5-L complexes, electron transfer from L to PF5 on forming these complexes also follows the order PMe3 > PPh3 ≈ AsMe3.

Synthesis, Structure and Antioxidant Activity of Mixed Ruthenium(III) Benzoyl Pyridine Complex

A new ruthenium arsine complex was prepared by reacting equimolar ratio of [RuBr3(AsPh3)3] and 2-benzoyl pyridine. It was characterized by microanalysis, FT-IR and single crystal X-ray diffraction studies. X-ray diffraction data showed the distorted octahedral geometry of the complex. The pyridine nitrogen and carbonyl oxygen of the ligand coordinated with the metal center. Antioxidant activity of the complex was analyzed using different assays, which manifested significant activity. It has been found that a newly synthesized complex possessed better antioxidant activity than the ligand and precursor complex.

Neutral and cationic phosphine and arsine complexes of tin(iv) halides: synthesis, properties, structures and anion influence.

The reaction of trans-[SnCl4(PR3)2] (R = Me or Et) with trimethylsilyltriflate (TMSOTf) in CH2Cl2 solution substitutes one chloride to form [SnCl3(PR3)2(OTf)]; addition of excess TMSOTf does not substitute further chlorides. The complexes have been fully characterised by microanalysis, IR and multinuclear NMR (1H, 13C{1H}, 19F{1H}, 31P{1H}, 119Sn) spectroscopy. The crystal structure of [SnCl3(PMe3)2(OTf)] revealed mer-chlorines and trans-phosphines. In contrast, trans-[SnBr4(PR3)2], [SnCl4{Et2P(CH2)2PEt2}], [SnCl4{o-C6H4(PMe2)2}] and [SnCl4{o-C6H4(AsMe2)2}] did not react with TMSOTf in CH2Cl2 solution even after 3 days. The arsine complexes, [SnX4(AsEt3)2] (X = Cl, Br), were confirmed as trans-isomers by similar spectroscopic and structural studies, while attempts to isolate [SnI4(AsEt3)2] were unsuccessful and reaction of SnX4 with SbR3 (R = Et, iPr) resulted in reduction to SnX2 and formation of R3SbX2. trans-[SnCl4(AsEt3)2] is converted by TMSOTf into [SnCl3(AsEt3)2(OTf)], whose X-ray structure reveals the same geometry found in the phosphine analogues, with the triflate coordinated. The salts, [SnCl3(PEt3)2][AlCl4] and [SnCl2(PEt3)2][AlCl4]2 were made by treatment of [SnCl4(PEt3)2] with one and two mol. equivalents, respectively, of AlCl3 in anhydrous CH2Cl2, whereas reaction of [SnCl4(AsEt3)2] with AlCl3 produced a mixture including Et3AsCl2 and [Et3AsCl][Sn(AsEt3)Cl5] (the latter identified crystallographically). In contrast, using Na[BArF] (BArF = [B{3,5-(CF3)2C6H3}4]-) produced [SnCl3(PEt3)2][BArF] and also allowed clean isolation of the arsine analogue, [SnCl3(AsEt3)2][BArF]. [SnCl4{o-C6H4(PMe2)2}] also reacts with AlCl3 in CH2Cl2 to form [SnCl3{o-C6H4(PMe2)2}][AlCl4] and [SnCl2{o-C6H4(PMe2)2}][AlCl4]2. Multinuclear NMR spectroscopy on the [AlCl4]- salts show that δ31P and δ119Sn move progressively to high frequency on conversion from the neutral complex to the mono- and the di-cations, whilst 1J(119Sn-31P) follow the trend: [SnCl3{o-C6H4(PMe2)2}]+ > [SnCl4{o-C6H4(PMe2)2}] > [SnCl2{o-C6H4(PMe2)2}]2+. DFT studies on selected complexes show only small changes in ligand geometries and bond lengths between the halide and triflate complexes, consistent with the X-ray crystallographic data reported and the HOMO and LUMO energies are relatively unperturbed upon the introduction of (coordinated) triflate, whereas the energies of both are ca. 4 eV lower in the cationic species and reveal significant hybridisation across the pnictine ligands.

Six-coordinate NbF5 and TaF5 complexes with tertiary mono-phosphine and -arsine ligands

The syntheses of the extremely moisture sensitive, neutral [MF5(PR3)] (M = Nb or Ta, R = Me or Ph) and [MF5(AsR′3)] (R′ = Me or Et), from reaction of the ligands with MF5 in anhydrous diethyl ether solution are reported. Attempts to isolate analogous complexes with SbMe3 were unsuccessful. The products are characterised by IR and mutinuclear NMR (1H, 19F{1H}, 31P{1H} and 93Nb) spectroscopic studies. These are the first examples of six-coordinate phosphine or arsine complexes of the Group 5 pentafluorides. The ionic species, trans-[MF4(PMe3)2][MF6], are obtained from diethyl ether solution of [MF5(PMe3)] containing excess PMe3 and similarly characterised. All complexes are extremely moisture and oxygen sensitive and decomposed by many common solvents. In solution in toluene the [MF5(PMe3)] (M = Nb or Ta) and [MF5(AsR′3)] are extensively dissociated at ambient temperatures. The [MF5(PPh3)] dissolve in CH2Cl2 with decomposition to form [PPh3H][MF6]. Attempts to isolate phosphine complexes of NbOF3 were unsuccessful.

Yttrium Complexes of Arsine, Arsenide, and Arsinidene Ligands

AbstractDeprotonation of the yttrium–arsine complex [Cp′3Y{As(H)2Mes}] (1) (Cp′=η5‐C5H4Me, Mes=mesityl) by nBuLi produces the μ‐arsenide complex [{Cp′2Y[μ‐As(H)Mes]}3] (2). Deprotonation of the AsH bonds in 2 by nBuLi produces [Li(thf)4]2[{Cp′2Y(μ3‐AsMes)}3Li], [Li(thf)4]2[3], in which the dianion 3 contains the first example of an arsinidene ligand in rare‐earth metal chemistry. The molecular structures of the arsine, arsenide, and arsinidene complexes are described, and the yttrium–arsenic bonding is analyzed by density functional theory.

Yttrium complexes of arsine, arsenide, and arsinidene ligands.

Deprotonation of the yttrium–arsine complex [Cp′3Y{As(H)2Mes}] (1) (Cp′=η5-C5H4Me, Mes=mesityl) by nBuLi produces the μ-arsenide complex [{Cp′2Y[μ-As(H)Mes]}3] (2). Deprotonation of the As–H bonds in 2 by nBuLi produces [Li(thf)4]2[{Cp′2Y(μ3-AsMes)}3Li], [Li(thf)4]2[3], in which the dianion 3 contains the first example of an arsinidene ligand in rare-earth metal chemistry. The molecular structures of the arsine, arsenide, and arsinidene complexes are described, and the yttrium–arsenic bonding is analyzed by density functional theory.

Soft diphosphine and diarsine complexes of niobium(v) and tantalum(v) fluorides: synthesis, properties, structures and comparisons with the corresponding chlorides

The reactions of the soft diphosphines o-C6H4(PMe2)2, Me2P(CH2)2PMe2, Et2P(CH2)2PEt2 or o-C6H4(PPh2)2 with NbF5 or TaF5 in anhydrous MeCN solution produce [MF4(diphosphine)2][MF6] (M = Nb or Ta), which have been characterised by microanalysis, IR, (1)H, (19)F{(1)H}, (31)P{(1)H} and (93)Nb NMR spectroscopy. X-ray crystal structures are reported for the isomorphous [MF4{o-C6H4(PMe2)2}2][MF6], which confirm the presence of eight-coordinate (distorted dodecahedral) cations. The corresponding reactions using o-C6H4(AsMe2)2 produced [MF4{o-C6H4(AsMe2)2}2][MF6] which were similarly characterised, including by the X-ray structure of [NbF4{o-C6H4(AsMe2)2}2][NbF6]. These are very rare examples of arsine complexes of high valent metal fluorides. The chloro complexes [NbCl4{o-C6H4(PMe2)2}2]Cl, [TaCl4{o-C6H4(PMe2)2}2][TaCl6], [NbCl4{Me2P(CH2)2PMe2}2][NbCl6] and [MCl4{o-C6H4(AsMe2)2}2][MCl6] were prepared and their structural and spectroscopic properties compared with the fluoride analogues. Attempts to prepare diphosphine complexes of NbOF3 were unsuccessful, but the NbOCl3 complexes, [{{Me2P(CH2)2PMe2}NbOCl3}2{μ-Me2P(CH2)2PMe2}] and [{o-C6H4(PMe2)2}NbOCl3(μ-O)NbCl3(CH3CN){o-C6H4(PMe2)2}] were obtained. X-Ray structures are also reported for [NbCl4{o-C6H4(PMe2)2}2]Cl, [NbCl4{o-C6H4(AsMe2)2}2][NbCl5(OEt)], [NbCl4{o-C6H4(PMe2)2}2][NbOCl4(CH3CN)], [{{Me2P(CH2)2PMe2}NbOCl3}2{μ-Me2P(CH2)2PMe2}] and [{o-C6H4(PMe2)2}NbOCl3(μ-O)NbCl3(CH3CN){o-C6H4(PMe2)2}].

Syntheses, X-ray structures and CVD of titanium(iv) arsine complexes

Five titanium arsine compounds have been synthesised via the reaction of TiCl(4) with AsPh(3) (1 : 1 and 1 : 2 equivalents), or one equivalent of Ph(2)AsCH(2)AsPh(2), (t)BuAsH(2) and As(NMe(2))(3). In general, 1 : 1 and 1 : 2 adducts of the type [TiCl(4)(L)(n)] (n = 1, L = AsPh(3), Ph(2)AsCH(2)AsPh(2), and (t)BuAsH(2); n = 2, L = AsPh(3)), were isolated and characterised. However, the reaction of TiCl(4) with As(NMe(2))(3) resulted in a novel exchange between a Cl and an NMe(2) group, yielding the product [TiCl(3)(NMe(2))(mu-NMe(2))(2)AsCl]. The crystal structure of [TiCl(3)(NMe(2))(mu-NMe(2))(2)AsCl] has been determined and showed that the titanium and arsenic atoms are linked via two bridging NMe(2) groups. Additionally, crystal structures for the 1 : 1 and 1 : 2 adducts, [TiCl(4)(AsPh(3))] and [TiCl(4)(AsPh(3))(2)] have been obtained, with Ti-As bond lengths of 2.7465(13) and 2.7238(7) A observed respectively. The decomposition of the compounds has been investigated using thermogravimetric analysis, aerosol-assisted and low pressure chemical vapour deposition.

Contrasting arsine and phosphine coordination behaviour: heteroleptic palladium(II) complexes with triphenylarsine and a crown thioether

The synthesis, spectroscopic data and crystal structures of two new mononuclear Pd(II) heteroleptic complexes with the crown trithioether 1,4,7-trithiacyclononane (9S3) and the arsine ligand, triphenylarsine (AsPh3) are presented. Reaction between [Pd(9S3)Cl2] and AsPh3 (1:2 stoichiometry) in nitromethane followed by metathesis to the hexafluorophosphate salt results in the formation of two different palladium(II) complexes, the expected bis arsine complex [Pd(9S3)(AsPh3)2](PF6)2 as well as, surprisingly, the intermediate mono arsine-chloro complex [Pd(9S3)(AsPh3)(Cl)](PF6). Both complexes exhibit the anticipated structure consisting of a cis square planar array of two sulfur atoms from the 9S3 and either two As donors (bis AsPh3 complex) or one As and one Cl donor (mono AsPh3 complex). The third 9S3 sulfur atom exhibits a long distance interaction with the palladium forming an elongated square pyramidal geometry with a coordination environment around the Pd best described as [S2As2 + S1] or [S2AsCl + S1]...

Synthesis and NMR Studies of [(C5Me5)Os(L)H2(H2)+] Complexes. Evidence of the Adoption of Different Structures by a Dihydrogen Complex in Solution and the Solid State

Protonation of the osmium(IV) trihydrides (C5Me5)OsH3(L) with HBF4 in diethyl ether affords the molecular dihydrogen complexes [(C5Me5)Os(H2)H2(L)][BF4], where L is PPh3 (1), AsPh3 (2), or PCy3 (3). Ruthenium analogues of these species are not stable and instead lose H2 readily. These compounds adopt four-legged piano-stool geometries in which the phosphine ligand is “trans” to an elongated dihydrogen ligand. For 1 and 2, the coordinated H2 ligand is oriented with its H−H vector nearly parallel with the Os−Ct vector, where Ct is the centroid of the C5Me5 ring; in contrast, in 3 the H2 ligand is oriented with its H−H vector perpendicular to the Os−Ct vector. In the 1H NMR spectra, exchange between the Os−H and Os−H2 environments can be slowed at low temperatures for the arsine complex 2 (but not for 1 or 3), and separate resonances could be observed for the hydride and dihydrogen sites; the barrier for exchange is approximately 6.0 kcal/mol. Partially deuterated samples were prepared, and H−H distances within the bound H2 ligands were deduced from the observed 1JHD(av) coupling constants. In addition, H−H distances were deduced from the T1(min) values for the osmium-bound hydrogen atoms, after correction for exchange and ligand-induced dipolar relaxation effects. In all cases, the two solution measurements were in agreement but differed from that deduced from neutron diffraction data. Specifically, for 1 the solution data gave a distance of ca. 1.07 vs 1.01 Å in the solid state; similarly, for 2 the solution value of ca. 1.15 Å was longer than the 1.08 Å value seen in the solid state. In both cases, the ∼0.06 Å lengthening in solution, if real, is the result most likely of one or both of two factors: the effect of removing the BF4 counterion from the vicinity of the cation and the effect of librational motion that tends to shorten artificially H−H distances deduced from neutron diffraction data. In contrast, for 3 the solution H−H distance of ca. 1.12 Å is significantly shorter than the 1.31 Å distance determined from the neutron diffraction data. DFT calculations support the hypothesis that different structures are adopted by 3 in solution and in the solid state and that in solution an equilibrium is established between two dihydrogen−dihydride structures, one with a considerably shorter H−H bond than is seen in the solid state.

Crystal structures and luminescence properties of osmium complexes of cis-1,2-vinylenebis(diphenylarsine) and pyridyl ligands: Possible evidence for metal d, ligand d backbonding

Divalent osmium complexes of the form [ Os ( N – N ) 2 L – L ] ( PF 6 - ) 2 where N–N was a polypyridyl, and L–L was either cis-1,2-bis(diphenylphosphino)ethene (dppene) or cis-1,2-vinylenebis(diphenylarsine) (dpaene) have been synthesized and characterized. X-ray structures were determined for three complexes and for the free dpaene molecule. It was observed that the P–C bond lengths, and C–P–C bond angles do not change significantly when complexed to osmium. It was observed the As–C bond lengths shorten by 2.3 pm and the C–As–C bond angles broaden by 5.6° when dpaene was complexed to osmium. These changes in the arsine structure may indicate a different method of backbonding between arsenic and osmium. It was found that the arsine complexes had absorption and emission that were to the red of analogous phosphine complexes. In violation of “energy gap law”, the dpaene complexes were found to have higher quantum yields. This may be due to the way that the arsenic atoms bond to osmium.

Pulsed-field ionization zero electron kinetic energy spectroscopy and theoretical calculations of copper complexes: Cu–X(CH3)3 (X=N,P,As)

The copper complexes were produced in pulsed laser vaporization molecular beams and investigated by pulsed-field ionization zero electron kinetic energy (ZEKE) spectroscopy and second-order Møller–Plesset (MP2) perturbation and hybrid B3LYP density functional theory calculations. The ground electronic states of Cu–X(CH3)3 and Cu+–X(CH3)3 (X=N,P,As) are A12 and A11, respectively, both with C3v symmetry. From the ZEKE spectra, the adiabatic ionization potentials of the neutral molecules are determined to be 44 730, 41 508, and 42 324 cm−1, and the Cu+/Cu–X stretching frequencies are 268/199, 214/187, and 188/155 cm−1 for X=N, P, and As, respectively. The degenerate Cu+/Cu–P–C and Cu+/Cu–As–C bending frequencies are measured to be 146/83 and 118/52 cm−1, while the Cu+/Cu–N–C mode was not observed. In addition, the CH3 wag, X–C stretching, and XC3 umbrella modes are also measured for the phosphine and arsine complexes. From the MP2 theory, the dissociation energies of the Cu+ and Cu complexes are estimated to be 59/12, 70/15, and 65/11 kcal mol−1 down the X group. Both MP2 and B3LYP predictions of ionic vibrational frequencies compare well with the spectroscopic values, but the B3LYP calculations of neutral low frequency modes are less satisfactory. On the other hand, the B3LYP calculations yield better ionization potentials than the MP2 methods for these molecules.

Oxorhenium(V) complexes with bis-phosphinite chelating coligands. The crystal structure of [ReOCl 2(OMe)L 1], [ReOCl 3L 2], [ReOCl 2(OEt)L 2] and [ReOCl 2{Ph 2PO(CH 2) 2O}{PPh 2(OEt)}] [L 1=Cy 2PO(CH 2) 2OPCy 2, L 2=Ph 2PO(CH 2) 2OPPh 2

The new ligand 1,2-bis(dicyclohexylphosphinite)ethane ( L 1) was prepared by reaction of ethylenglycol with dicyclohexylphosphine in the presence of triethylamine. By treating this ligand with the arsine complex [ReOCl 3(AsPh 3) 2] and trituring the formed oil with methanol, the complex [ReOCl 2(OMe)L 1] ( 1) was isolated and its crystal structure was studied by X-ray diffractometry. The coordination sphere around the Re atom is a pseudo-octahedron. The crystal structure of the previously reported complex [ReOCl 3L 2] ( 2) (L 2=1,2-bis[diphenylphosphinite]ethane) was solved by X-ray diffractometry. When Complex 2 was refluxed in EtOH, the oxo-alkoxide complex [ReOCl 2(EtO)L 2] ( 3) was formed by a metathesis reaction. X-ray diffraction studies of Complex 3 show a pseudo-octahedral geometry around the Re atom with the oxo and ethoxy groups mutually trans. Finally, reaction of 2 with the monodentate phosphinite PPh 2(OEt) ligand yielded the paramagnetic Re(III) compound [ReCl 3L 2{PPh 2(OEt)}] (previously reported) and the new unexpected Re(V) by-product [ReOCl 2(Ph 2POCH 2CH 2O){PPh 2(OEt)}] ( 4). On the contrary, compounds 1 and 3 did not react with PPh 2(OEt) under the same conditions.

Tri(allyl)- and tri(methylallyl)arsine complexes of palladium(ii) and platinum(ii): synthesis, spectroscopy, photochemistry and structures

Tri(allyl)- and tri(methylallyl)arsine complexes of palladium(II) and platinum(II) with the formulae [MX2L2] (M=Pd, Pt and X=Cl, Br, I): [Pd2Cl2(μ-Cl)2L2], [PdCl(S2CNEt2)L] and [Pd2Cl2(μ-dmpz)2L2] [L=As(CH2CHCH2)3 (L′), As(CH2CMeCH2)3 (L″), dmpz=3,5-dimethylpyrazolate] have been prepared. All the complexes have been characterized by elemental analyses and by IR and NMR (1H, 13C, 195Pt) spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The molecular structures of complexes [MX2{As(CH2CHCH2)3}2] (M=Pd, X=Cl or Br), [MX2{As(CH2CMeCH2)3}2] (M=Pd, X=Cl or Br; M=Pt, X=Cl) and [Pd2Cl2(μ-Cl)2{As(CH2CMeCH2)3}2] have been established by single crystal X-ray diffraction analyses. The mononuclear complexes exclusively adopt the trans configuration with the exception of [PdCl2L″2], which could be isolated as cis and trans isomers. In the binuclear derivative the arsine ligands are attached to an envelope-shaped Pd–(μ-Cl)2–Pd rectangle with a trans (anti) orientation towards each other. The mononuclear complexes are slightly photoreactive upon irradiation in their long-wavelength absorption band.

The trans effect and trans influence of triphenyl arsine in platinum(ii) complexes. A comparative mechanistic and structural study

The kinetics and mechanism of the reaction between [PtI3(AsPh3)](-) and pyridine in acetonitrile solvent has been studied by use of stopped-flow spectrophotometry. Substitution of iodide trans to arsine is irreversible under the conditions used and takes place via parallel direct and solvolytic pathways. By comparing the rate constants of the direct pathway with literature values of the corresponding phosphine and stibine complexes the following trans effect series can be obtained: Ph3Sb > Ph3P > Ph3As. The crystal and molecular structures of reactant and product have been determined. Based on Pt-I distances for the investigated arsine complex and literature data for the corresponding phosphine and stibine complexes the following trans influence series was derived: Ph3P greater than or equal to Ph3As > Ph3Sb. To the best of our knowledge this is the first comparison of all the three heavier pnictogens as donor atoms using strictly analogous complexes with identical cis-ligands.

Cis-dichlorobis(triethylarsine)platinum(II) and cis-dichlorobis(triethylphosphine)platinum(II).

The crystal structure of cis-[PtCl2(C6H15As)2], (I), is isostructural with a previously reported structure of cis-[PtCl2(C6H15P)2], (II). A new polymorph of (II) is also reported here. Selected geometrical parameters in the arsine complex are Pt-Cl 2.3412 (12) and 2.3498 (13), Pt-As 2.3563 (6) and 2.3630 (6) A, Cl-Pt-Cl 88.74 (5), As-Pt-As 97.85 (2), and Cl-Pt-As 171.37 (4) and 177.45 (4) degrees. Corresponding parameters in the phosphine complex are Pt-Cl 2.364 (2) and 2.374 (2), Pt-P 2.264 (2) and 2.262 (2) A, Cl-Pt-Cl 85.66 (9), P-Pt-P 98.39 (7), and Cl-Pt-P 170.26 (7) and 176.82 (8) degrees.

Applications of Pulsed Field Gradient Spin−Echo Measurements to the Determination of Molecular Diffusion (and Thus Size) in Organometallic Chemistry

Pulsed field gradient spin−echo (PGSE) measurements on (a) four arsine complexes of Pd(II), PdCl2L2 (L = AsMexPh3-x (x = 3−0)), (b) three different ferrocene phosphine dendrimers, and (c) a selecti...

Ligand to ligand charge transfer in (hydrotris(pyrazolyl)borato)(triphenylarsine)copper(I).

Emission and UV-vis absorption spectra of (hydrotris(pyrazolyl)borato)(triphenylarsine)copper(I), (CuTpAsPh3), (hydrotris(pyrazolyl)borato)(triethylamine)copper(I), (CuTpNEt3), and (hydrotris(pyrazolyl)borato)(triphenylphosphine)copper(I), (CuTpPPh3), are reported. The spectra of the arsine complex contain low-energy bands (with a band maximum at 16,500 cm(-1) in emission and a weak shoulder centered at about 25,000 cm(-1) in absorption) that are not present in the corresponding spectra of the amine or phosphine complexes. The lowest energy electronic transition is assigned to ligand to ligand charge transfer (LLCT) with some contribution from the metal. This assignment is consistent with PM3(tm) molecular orbital calculations that show the HOMO to consist primarily of pi orbitals on the Tp ligand (with some metal orbital character) and the LUMO to be primarily antibonding orbitals on the AsPh3 ligand (also with some metal orbital character). The absorption shoulder shows a strong negative solvatochromism, indicative of a reversal or rotation of electric dipole upon excitation, and consistent with a LLCT. The trends in the energies of the electronic transitions and the role of the metal on the LLCT are discussed.

A spectroscopic, electrochemical and structural study of polarizable, dipolar ruthenium(II) arsine complexes as models for chromophores with large quadratic non-linear optical responses

The new series of complex salts trans-[RuIICl(pdma)2L][PF6]2 [pdma = 1,2-phenylenebis(dimethylarsine); L = N-methyl-4,4′-bipyridinium (MeQ+) 2, N-phenyl-4,4′-bipyridinium (PhQ+) 3, N-(4-acetylphenyl)-4,4′-bipyridinium (4-AcPhQ+) 4, N-(2,4-dinitrophenyl)-4,4′-bipyridinium (2,4-DNPhQ+) 5 or N-(2-pyrimidyl)-4,4′-bipyridinium (2-PymQ+) 6] have been prepared. The known complex salt trans-[RuIICl(pdma)2(4,4′-bpy)]PF6 (4,4′-bpy = 4,4′-bipyridine) 1 exhibits an intense dπ(RuII)→π*(4,4′-bpy) metal-to-ligand charge-transfer (MLCT) absorption with λmax at 418 nm in acetonitrile, whilst 2–6 display dπ(RuII)→π*(L) MLCT bands with λmax values in the region 486–544 nm. The MLCT energy decreases as the electron-accepting ability of L increases, in the order L = MeQ+ < PhQ+ < 4-AcPhQ+ < 2,4-DNPhQ+ < 2-PymQ+. Cyclic voltammetric studies show that within the series 2–6, the energy of the Ru-based HOMO is almost constant, whilst that of the L-based LUMO decreases by ca. 0.4 eV moving from 2 to 6. Single-crystal structures of the complete series 1·DMF, 2, 3·MeCN, 4·Me2CO, 5·MeCN and 6 have been determined. Analysis of bond lengths and dihedral angles provides no evidence for ground state charge-transfer, despite the strongly dipolar, polarizable nature of these complexes.